Passive Solar Tracker for a Solar Concentrator

Abstract

The efficient operation of a solar concentrator requires the radiation collector to be pointed directly at the sun. The present invention represents one approach to a passive solar tracking system capable of focusing solar radiation onto a small target at all times of the year. The device consists of a two-axis gimbal system with its orientation controlled by interconnected ballasts filled with a volatile fluid. Accurate focusing is realized by ensuring that each significant mass element is balanced by another element of equal mass equidistant from and diametrically opposite to it through the point of intersection of the two gimbal axes for all possible orientations of the system.

1 . A passive solar tracker and concentrating system comprising 
 a. a two-axis gimbal system in which a pair of containers partially filled with a volatile fluid are affixed to two opposing sides of the frame attached to each of the two orthogonal axes, each of said pair being in fluidic communication by means of a connecting tube, and each of said containers being shielded by a shade, so that the equilibrium orientation of the gimbal system corresponds to that where the plane defined by the inner gimbal frame faces the sun normally as a result of each of said pairs of containers being equally irradiated by the sun;    b. a light concentrating element attached to said two-axis gimbal system, which focuses the incident solar radiation; and    c. a target which intercepts said focused solar radiation.    
     
     
         2 . A passive solar tracker and concentrating system according to  claim 1  wherein said containers holding said volatile fluid are segmented and each of the sub-chambers is in fluidic communication with the corresponding one on the opposite side of the associated axis by means of a connecting tube.  
     
     
         3 . A passive solar tracker and concentrating system according to  claim 2  wherein each of said sub-chambers is substantially filled with said volatile fluid.  
     
     
         4 . A passive solar tracker and concentrating system according to  claim 2  wherein said volatile fluid increases its vapor pressure by more than approximately 10 kPa per degree Celsius increase in its temperature.  
     
     
         5 . A passive solar tracker and concentrating system according to  claim 1  wherein said light concentrating element is a lens.  
     
     
         6 . A passive solar tracker and concentrating system according to  claim 5  wherein each significant mass element is balanced by an equal mass element positioned at a diametrically opposite location through the point where the two axes of the gimbal intersect.  
     
     
         7 . A passive solar tracker and concentrating system according to  claim 1  wherein said light concentrating element consists of a reflective dish and a mirror positioned in front of the focus of the dish.  
     
     
         8 . A passive solar tracker and concentrating system according to  claim 7  wherein the reflective dish has a parabolic shape.  
     
     
         9 . A passive solar tracker and concentrating system according to  claim 7  wherein each significant mass element is balanced by an equal mass element positioned at a diametrically opposite location through the point where the two axes of the gimbal intersect.  
     
     
         10 . A passive solar tracker and concentrating system according to  claim 1  wherein said target is an optical fiber or fiber bundle.  
     
     
         11 . A passive solar tracker and concentrating system according to  claim 1  wherein said target is a solar panel.  
     
     
         12 . A passive solar tracker and concentrating system according to  claim 1  wherein said target is a thermally driven engine such as a Stirling engine.